Christmas in Australia arrived right as households enter their highest-energy stretch of the year. Air conditioners run longer, kitchens work overtime, and many homes welcome a steady flow of guests—all while heatwaves push electricity demand to its peak. Even with good rooftop solar, late-afternoon gatherings, evening cooking, and extra hot-water use often push families back onto the grid when prices are at their toughest.
The good news is that most of the holiday bill shock is avoidable. With a few smart adjustments to timing, appliance use, and how you plan for the hottest parts of the day, it’s possible to stay comfortable, keep guests happy, and avoid an unexpected spike in costs. This guide breaks down practical, homeowner-ready ways to manage your energy use during the busiest weeks of summer, even if you don’t have a battery.
Understanding the holiday energy curve
December shifts how households use power, and the pattern is remarkably consistent every year. Air conditioning becomes the dominant load from mid-afternoon through to the evening, right at the point when solar generation starts to taper off. Kitchens also work harder with long oven sessions, induction cooking, and extra dishwasher cycles, stack together in hours when homes rely more heavily on the grid. Add in visiting family, extra showers, more laundry and a few bonus appliances plugged in around the house, and the result is a steep climb in total consumption.
A simple way to picture the problem is to compare when energy is used to when solar is available. Most holiday activities are after 4 pm, but most solar peaks occur between late morning and early afternoon. That mismatch is what drives December bill spikes for solar and non-solar households.
Typical holiday loads at home
- Air conditioning is working the hardest from 3pm onwards
- Cooking and dishwashing concentrated around dinner
- Hot-water recovery cycles after showers
- Pool pumps compete with cooling during hot days
- Decorations and extra lighting are adding a steady background load
Understanding this curve is the starting point for cutting holiday costs. Once homeowners can see where their energy goes, and when, it becomes far easier to move certain tasks into solar hours and reduce peak-time strain.
Optimising cooking and cooling around solar hours
The biggest issue in December is when appliances are used. Most cooking and cooling demand happens from 4 pm onwards.
To manage this, homeowners need to understand the real load behind the appliances they rely on during summer gatherings. Many of them draw far more power than people expect.
Where the heavy loads actually come from
The following appliances are all standard household devices, but they become major contributions to peak demand when several run together late in the day:
- Electric ovens typically draw 2,000-4,000W on high settings, making them one of the largest loads in the home during long cooking sessions.
- Induction cooktop zones use 1,800-2,300W on high settings, with short-term boosts even higher.
- Dishwashers often pull 1,500-2,000W during the heating cycle.
- Air fryers draw around 1,200-1,700W, though they heat quickly and use less energy overall than a full oven.
- Slow cookers, by contrast, run at just 150-300W, making them ideal for solar-powered all-day cooking.
How to shift cooking into solar-friendly hours
The goal during the holiday period is to schedule the biggest loads when your solar system can cover them:
- Finish long oven roasts by early afternoon and reheat briefly later.
- Prepare sides, desserts, and oven-heavy dishes between 11am and 3pm, when solar is strongest.
- Reserve late-afternoon cooking for low-wattage appliances like air fryers, microwaves, or slow cookers.
- Avoid running the oven + induction + AC together after 4 pm, which can instantly push a home from solar to grid reliance.
Cooling efficiently in summer conditions
Air conditioning is often the single biggest contributor to late-day demand. Evidence-based strategies include:
- Pre-cooling from 10 am-2 pm can reduce evening AC energy use by up to 25% according to CSIRO modelling
- Setting the thermostat at 23-24°C balances comfort and consumption; going lower can add 5-10% per degree.
- Clean filters before December, as blocked filters can reduce efficiency by 10-15%.
- Units with high Zones Energy Rating Label (ZERL) scores perform better during 30-40°C summer days.
When the heaviest loads run in the early afternoon, solar handles most of the work. When they run at 5pm, the grid does — and that’s the difference between a manageable December bill and a summer-season surprise.
Using your hot-water heat pump as a “thermal battery”
Hot-water systems quietly become one of the biggest energy users over the Christmas period. Extra showers, extra laundry, and hotter outdoor temperatures can trigger your heat pumps to cycle more often, sometimes late in the day when solar production is minimal, and tariffs are higher.
Most don’t realise that a heat-pump hot-water system is effectively a thermal battery. If it’s timed correctly, it can store cheap or solar-powered heat during the middle of the day and avoid running when you’re relying on the grid.
Why timing matters
A modern heat pump system typically draws 700-1,200W per heating cycle. Shifting the system into solar hours means the same hot water is produced, but without the grid cost.
Recommended timer settings for summer
If your system has a timer or smart controller, set it to:
- Start heating between 11am and 3pm, when solar is peaking
- Disable or limit evening boosts, unless absolutely necessary
- Allow an early-morning top-up only on high-use days, such as when multiple guests are staying
These settings cover most household patterns while keeping the system aligned with solar availability.
Increasing tank temperature safely
Some may benefit from raising the tank temperature slightly before big holiday gatherings. A higher set point increases your stored hot-water “capacity,” reducing the need for evening reheats.
Safe guidelines:
- Standard storage temperature is 60°C (required to prevent Legionella).
- Increasing 65°C is generally safe but should be done according to the manufacturer’s instructions.
- Homes with young children or elderly residents should use mixing valves to maintain safe tap temperatures.
Why heat pumps outperform electric storage systems in December
Older electric storage systems use 3,000-4,000W heating elements. When they switch on at 5pm, they can single-handedly push your household into peak demand.
A heat pump, by comparison:
- Uses about one-third of the energy
- Performs better in warm summer air
- Aligns more naturally with solar generation
- Reduces evening load without reducing comfort
Quick homeowner check
Before the holiday period, it’s worth confirming:
- Your heat pump timer is enabled
- Your tank is large enough for extra guests
- There’s no late-afternoon boost cycle enabled by default
- The system is set to heat during solar hours, not after them
Small adjustments in timing can cut December water heating costs dramatically without changing anyone’s shower habits. The goal is simply to produce hot water when your home is generating power.
Automating appliances for solar-first energy use
Even without a battery of a complex smart-home setup, simple automations can shift a surprising amount of energy into the solar window. December is the ideal time to use them because appliances run longer and more often, which means automation delivers bigger savings than at any other time of year.
How much load can you realistically shift
Many underestimate how much discretionary demand can be moved into the 10am-3pm solar peak. During summer and holiday hosting, these loads are easier to automate:
- Dishwasher (1.0-1.5 kWh per cycle)
- Washing machine (0.5-1.0 kWh)
- Heat-pump dryer (0.7-1.5 kWh)
- Pool pump (0.6-1.2 kWh midday vs late afternoon)
- Fans and circulation systems (~50-70W each)
Automating even two or three of these can shift 3-5 kWh per day into the solar window during the busiest weeks of summer.
Affordable devices that make automation easy
Most households don’t need a full home energy management system. A few low-cost tools can deliver meaningful results:
- Smart plugs with scheduling (ensure they support at least 10A or 15A, depending on the appliance)
- Smart timers for heat-pump hot water
- Split-system AC with built-in scheduling or app-based control
- Pool pump controllers that integrate with daily solar windows
- Inverter apps that track generation so homeowners can adjust schedules in real time
For safety and compliance, avoid plugging high-wattage appliances (like ovens, induction cooktops, or resistive heaters) into smart plugs unless they are specifically rated for the load, most aren’t.
Practical holiday-ready automations
These changes matter most when the home is hosting guests or running multiple appliances at once:
- Set dishwashers to run between 11am and 2pm, ideally after lunch preparation
- Schedule washing machines before midday, especially after guest stays
- Program heat-pump dryers to run at 1-3 pm, when solar is strongest
- Automate pool pumps to run almost exclusively in the early afternoon
- Use fan schedules to circulate air during solar hours, reducing late-day AC load
AC timers for peak heat
Smart AC controls are one of the highest-value summer automations:
- Start pre-cooling late morning so the AC doesn’t need to run continuously at 5pm.
- Limit evening run times using automated comfort schedules (e.g., 5-7 pm only).
- Create zone-specific schedules so only high-use rooms get cooled.
Avoiding the biggest hosting mistakes that drive up summer bills
Even well-prepared households often fall into a handful of habits that quietly raise their energy use during the holiday period. These mistakes aren’t dramatic on their own, but when they occur on a 35-degree day with multiple appliances running, they can trigger the exact kind of late-afternoon demand spike most families want to avoid.
One of the most common issues is leaving exterior doors open while the air conditioner is running, especially during gatherings where people move in and out. Modern split systems are efficient, but they’re not designed to cool a constantly changing air volume. Every degree of hot air that enters the home forces the unit to work harder, particularly in the evening when solar has faded, and grid reliance is high. Closing blinds on west-facing windows and keeping doors shut between rooms helps stabilise the indoor environment.
Another frequent problem is the bonus fridge or freezer in the garage, which becomes a hidden energy drain in summer. In a 35-40°C garage, these appliances can run almost continuously, using up to 3 or 4 times as much power as in winter. Where possible, place drinks and holiday food in the main kitchen fridge, or pre-chill items earlier in the day when solar is strongest.
Bathrooms can also play a role in unnecessary demand. Heat lamps, often used by guests after showers, draw around 250-275W per globe. Four-lamp units can easily add a kilowatt to your evening load. Encouraging guests to use standard lights or limiting heat lamp use to colder mornings helps keep this under control.
Pool pumps are another culprit. Running a standard 1kW pump at 5pm relies almost entirely on grid power, whereas the midday cycle may be covered by solar. Shifting filtration or heating cycles to early afternoon can significantly reduce costs without compromising water quality.
Ceiling fans are efficient, but many households use them incorrectly. For summer, blades should rotate counterclockwise to create a cooling breeze. Using the winter rotation (clockwise) simply circulates warm air without improving comfort, causing people to increase AC usage unnecessarily.
These subtle behaviours add up quickly during the busiest weeks of the year. Adjusting them requires little effort, but the impact on comfort and energy bills can be substantial. If homeowners can eliminate even one or two of these habits, their household is far less likely to experience the typical summer bill surge.
Preparing your solar and inverter for peak summer conditions
December should be your strongest solar month, but heat, shading and system behaviour can quietly hold your output back. A few targeted checks before the holiday period can quickly reveal where performance is being lost.
Here’s what homeowners should look for:
- Heat-related output drops: Solar panels can lose 10-15% efficiency on 38-40°C days, and inverters may throttle if their internal temperature rises too high. Make sure nothing is blocking airflow around the inverter and that it isn’t exposed to unnecessary direct heat.
- New summer shading: Trees in full growth or changing sun angles can create shadows that didn’t exist in winter. Even small patches of shade can drag down the entire string. Check for new shading at several points during the day.
- Monitoring app warnings: Sudden dips on clear days, one string lagging behind the other, or sharp drop-and-recover patterns may indicate a loose connector, early panel failure, or intermittent fault. These require an installer but are easy for a homeowner to spot early.
- Export limiting: If your generation curve suddenly hits a flat ceiling earlier than usual. Your DNSP may be applying dynamic export limits. This isn’t a system fault, but it affects how much solar gets clipped versus self-consumed.
- Inverter surroundings: Holiday decor, storage boxes, garden tools, or leaf debris can restrict ventilation without homeowners realising. Keeping the area clear helps the inverter stay within its operating temperature range.
These checks take only a few minutes but can recover valuable kilowatt-hours during the weeks when households rely most on their solar system.
Using a battery strategically — and why you don’t need one to manage Christmas demand
Batteries can take a lot of pressure off the grid during summer evenings, but even without one, most households can still avoid the typical December bill spike with the right timing. The key difference is how each home manages the late-afternoon period when solar drops and cooling, cooking, and hosting activity peaks.
For homes with a battery, the goal is to expand the amount of stored energy available for the 4pm-9pm window. That usually means adjusting reserve settings in your battery or inverter app so the system holds back more charge rather than exporting it during the day. A higher reserve helps cover evening cooling loads, especially on 35-40°C when air conditioners run continuously. If your battery supports time-based modes, set it to prioritise solar charging and restrict evening discharge to essential loads only.
If you don’t have a battery, you can replicate part of this benefit through load shifting. Running dishwashers, washing machines, dryers, heat pumps, and even some food prep during the solar window can free up several kilowatt-hours that would otherwise be pulled from the grid after sunset. Pre-cooling in the early afternoon replaces the need for long AC runtimes in the evening. For many households, this strategy alone eliminates most of the peak period bill shock.
It’s also worth knowing when a battery becomes genuinely useful. For homes with high evening cooling demand, a pool pump, or multiple induction appliances running together, storage can help smooth out the load profile. But for low-to-average users, especially those who already time their appliances around solar, the biggest December gains often come from behaviour rather than hardware.
The takeaway is simple: batteries are helpful, but not essential, for managing Christmas demand. Whether you have storage or not, the most reliable savings come from reshaping how your home uses energy.
The quick Christmas energy checklist
Small changes during December can prevent a late-afternoon surge that normally drives holiday bill spikes. These are the highest-value actions of households during the busiest weeks of summer:
- Pre-cool the house between 10am and 2pm so the air conditioner doesn’t need to run continuously at 5pm.
- Run dishwashers, washing machines, and heat pump dryers in the middle of the day, when solar is strongest.
- Finish long over or induction cooking sessions by early afternoon, using only quick reheats later.
- Find and remove any new summer shading on panels that has appeared due to tree growth or sun-angle changes.
- Shift pool pump cycles to early afternoon instead of the early-evening window.
- Check inverter ventilation and clear any decorations, boxes, or garden items blocking airflow.
- Confirm heat pump timers so hot water is generated during solar hours, not at night.
- Keep doors and blinds closed to stabilise indoor cooling and reduce AC load.
- Minimise evening use of energy-intensive extras, such as bathroom heat lamps or garage fridges, during peak outdoor temperatures.
These simple actions take little time but can recover several kilowatt-hours a day, enough to turn the holiday period from a stressful billing season into one of the easiest energy months to manage.
Managing energy demand over Christmas doesn’t require major upgrades or a full home overhaul. The biggest savings come from understanding when your household uses power and shifting the heaviest loads into the hours when your solar system is producing the most. With a few small changes to timing, appliance habits, and system checks, Australian homes can stay comfortable through the hottest weeks of summer without facing a holiday bill shock.
Energy Matters has been in the solar industry since 2005 and has helped over 40,000 Australian households in their journey to energy independence.
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